Method and apparatus for controlling electrolytic solution

ABSTRACT

An electrolytic solution control method can control the composition of an electrolytic solution efficiently with high precision, and can remove a partially decomposed product of an organic component from an electrolytic solution. The electrolytic solution control method includes storing an electrolytic solution containing an organic component and an inorganic component in an electrolytic solution storage tank while controlling and keeping the electrolytic solution at a predetermined composition, adjusting an inorganic component of the waste electrolytic solution after use in electrolytic processing in an electrolytic processing apparatus, and then returning the waste electrolytic solution to the electrolytic solution storage tank.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus for controlling electrolytic solution for controlling components of an electrolytic solution, such as a plating solution for use in the formation of interconnects by embedding of an interconnect material, such as copper, by plating into fine interconnect trenches and holes (via holes) formed in a surface of a substrate, such as a semiconductor substrate. The present invention is also applicable to control of an etching solution for etching an interconnect material by electrolytic etching, a similar electrolytic technique to plating.

2. Description of the Related Art

In the formation of fine interconnects using electroplating with copper sulfate for filling-in (embedding) of fine interconnect trenches and holes formed in the surface of a semiconductor substrate or the like, a copper sulfate plating solution is widely used which, in addition to the inorganic base components of copper sulfate (CuSO₄.5H₂O), sulfuric acid (H₂SO₄), chlorine (Cl), etc., comprises organic additives, such as an organic polymer compound as a so-called suppressor, a sulfur compound as a so-called accelerator, and a nitrogen compound as a so-called leveler in order to improve the quality of a plated film and enhance the trench/hole filling (embedding) property.

The organic components and the inorganic components of such a plating solution are partly consumed during its use in plating. Accordingly, in order to recover and reuse the plating solution (waste plating solution), it is necessary to adjust the components of the plating solution to a constant composition before reuse of the plating solution so as to stabilize the plating performance.

FIG. 9 schematically shows a conventional plating solution control system that employs a circulation method. As shown in FIG. 9, the plating solution control system includes a plating solution storage tank 12 for storing a plating solution 10 while keeping it at a predetermined composition. The plating solution storage tank 12 is connected to a plating apparatus 14 via a plating solution supply line 16 and a waste plating solution return line 18, so that the plating solution is allowed to circulate continuously between the plating solution storage tank 12 and the plating tank 14.

To the plating solution storage tank 12 is connected a base solution supply line 24 extending from a base solution storage tank 22 for storing a base solution 20 comprising a mixture of inorganic components, such as copper sulfate, sulfuric acid, hydrochloric acid and water in a predetermined proportion. An organic/inorganic component supply line 28 extending from an organic/inorganic component supply apparatus 26 is also connected to the plating solution storage tank 12. Further, a sampling line 30 for sampling the plating solution 10 from the plating solution storage tank 12 is connected at one end to the plating solution storage tank 12 and at the other end to an organic/inorganic component analyzer 32. An output signal from the organic/inorganic component analyzer 32 is fed back to the organic/inorganic component supply apparatus 26.

According to the plating solution control system, the plating solution 10 comprising a mixture of the base solution 20 with organic components in predetermined amounts is stored in the plating solution storage tank 12, and the plating solution 10 is supplied to the plating apparatus 14 to carry out plating. The organic and inorganic components of the plating solution are partly consumed during plating, and therefore the plating solution 10 in the plating solution storage tank 12 gradually runs short of part of the organic and inorganic components. Accordingly, the plating solution 10 in the plating solution storage tank 12 is sampled, and the organic and inorganic components of the plating solution 10 are analyzed by the organic/inorganic component analyzer 32. Based on the analytical results, the organic/inorganic component supply apparatus 26 is actuated to replenish the plating solution 10 with the shortage of organic/inorganic components so as to keep the plating solution 10 to be supplied to the plating apparatus 14 at a constant composition, thereby stabilizing the plating performance.

FIG. 10 schematically shows a conventional plating solution control system that employs a batch circulation method. This system differs from the system shown in FIG. 9 in that a recovery tank 36 for recovering a waste plating solution through a recovery line 34 connected to a plating apparatus 14, and a waste plating solution return line 38 connecting the recovery tank 36 and a plating solution storage tank 12 are provided so that the waste plating solution is once stored in the recovery tank 36 and the waste plating solution in the recovery tank 36 is returned intermittently to the plating solution storage tank 12.

FIG. 11 shows a conventional plating system which uses a plating solution in a one-pass manner without return and without control of the plating solution, that is, the plating solution is once used and thrown away. According to this system, a predetermined amount of base solution 20 is supplied from a base solution storage tank 22 through a base solution supply line 24 into a plating solution storage tank 12, and predetermined amounts of organic and inorganic components are supplied from an organic/inorganic component supply apparatus 26 through an organic/inorganic component supply line 28 into the plating solution storage tank 12, thereby preparing a plating solution 10 comprising predetermined components. The plating solution 10 in the plating solution storage tank 12 is supplied through a plating solution supply line 16 into a plating apparatus 14 to carry out plating, and the waste plating solution is discharged through a waste liquid line 40 and is subjected to waste liquid disposal.

The conventional plating solution control systems rely largely on organic/inorganic component analyzers that are complicated and costly, and are not fully satisfactory in analysis precision. It is, therefore, difficult to control the composition of a plating solution efficiently with high precision. In addition, the conventional control systems have the problem that a partially decomposed product of an organic component can accumulate in a plating solution.

Though the one-pass plating system has the advantage of no need for control of plating solution, such system involves the use of a larger amount of plating solution, leading to an increased cost, and also involves an increased amount of waste liquid to be disposed of.

While the conventional systems and attendant problems have been described in terms of a copper sulfate plating solution for use in plating to effect filling-in (embedding) of fine interconnect trenches and holes formed in the surface of a semiconductor substrate or the like, similar problems are involved in the use of other plating solutions comprising organic and inorganic components and also in the use of an electrolytic solution other than a plating solution, for example, an etching solution for use in etching processing.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above situation in the related art. It is therefore an object of the present invention to provide a method and an apparatus for controlling an electrolytic solution, which can control the composition of an electrolytic solution efficiently with high precision, and can remove a partially decomposed product of an organic component from an electrolytic solution.

In order to achieve the above object, the present invention provides an electrolytic solution control method comprising: storing an electrolytic solution containing an organic component and an inorganic component in an electrolytic solution storage tank while controlling and keeping the electrolytic solution at a predetermined composition; adjusting an inorganic component of the waste electrolytic solution after use in electrolytic processing in an electrolytic processing apparatus; and then returning the waste electrolytic solution to the electrolytic solution storage tank.

With respect to a copper-plating solution, for example, for use in copper plating in a plating apparatus having an insoluble anode or an electrolytic copper anode not containing phosphorus, the metal component (copper ions) of the copper-plating solution gradually decreases with the progress of plating. In this regard, an insoluble anode differs from a soluble anode, and cannot replenish copper ions consumed. In the case of an electrolytic copper anode, because of a disproportionation reaction caused by dissolved monovalent copper ions, a sufficient supply of divalent copper ions is not possible. Accordingly, it is necessary for reuse of the waste plating solution to replenish the inorganic component, copper ions. The shortage of copper ions can be inferred precisely from the integrated amount of electric current in the plating apparatus. By thus precisely inferring the shortage of copper ions, replenishing the waste plating solution with the shortage of copper ions, and returning the waste plating solution to a plating solution storage tank, it becomes possible to eliminate the use of an inorganic component analyzer for controlling a proper amount of copper ions to be replenished, and control copper ions in the plating solution efficiently with high precision.

In a preferred embodiment of the present invention, the adjustment of the inorganic component is effected by electrolytic processing carried out by providing a cathode chamber and an anode chamber which are separated by an ion exchanger, and using the waste electrolytic solution as an anode liquid.

To a plating liquid, replenishment of inorganic components, especially a metal component, is important. According to this embodiment, the replenishment of a metal component is effected by electrolytic processing utilizing electrolysis (anode dissolution). Thus, unlike the below-described method of adding metallic particles, there is no fear of particles or powder remaining in a plating solution, which particles (powder) are undesirable e.g. for the production of fine interconnects. Further, a metal component in a precise amount can be supplied to the waste plating solution. In the case of a copper-plating solution, for example, it is most appropriate to use phosphorus-containing copper for the anode. The phosphorus-containing copper herein refers to electrolytic copper doped with phosphorus in an amount of about 500 ppm. The use of an anode made of phosphorus-containing copper has the advantage of not generating monovalent copper ions that will cause a disproportionation reaction.

For replenishment of a metal component, besides the method that utilizes electrolysis, a method may be considered which involves dissolving a metal carbonate, a metal hydroxide or fine particles of a metal. This method, however, lacks reliability of a means for precisely weighing such metallic power or particles. In addition, the use of such powder or particles is not suitable for a plating solution which is employed e.g. for the production of fine interconnects.

Preferably, the ion exchanger is an ion-exchange membrane or ion-exchange fabric having monovalent cation selectivity.

By thus disposing an ion exchanger having monovalent cation selectivity, i.e. an ion exchanger, which selectively exchanges only monovalent cation ions, between a cathode and an anode, metal ions, such as divalent copper ions, supplied from the anode can be prevented from moving into the cathode chamber, whereby deposition of the metal on the cathode can be prevented. An ion-exchange membrane comprising a dense polymer membrane modified with, for example, a sulfonic group and also modified in the surface with, for example, quaternary ammonium, may be exemplified as an effective ion exchanger. The ion exchanger according to the present invention is, of course, not limited to such a polymer membrane.

When the present method is applied to replenishment of copper ions for a copper-plating solution, most cations movable to the cathode are hydrogen ions. Hydrogen ions, which have moved to the cathode, are converted into hydrogen gas at the cathode surface.

Preferably, a soluble electrode is used as an anode in the electrolytic processing of the waste electrolytic solution, and the current density at the anode is 10 to 100 mA/cm².

In the case of dissolving an anode, the current density at the anode is preferably set at a somewhat high value from the viewpoint of preventing the generation of e.g. monovalent copper ions. If the current density at the anode is made higher than 100 mA/cm², however, the anode dissolution efficiency can decrease due to generation of oxygen. The use of such a high current density is thus disadvantageous in the light of energy consumption. Accordingly, the current density at the anode is preferably within the range of 10-100 mA/cm².

Preferably, the concentration of metal ions in the waste electrolytic solution is detected during the electrolytic processing so as to adjust the amount of electric current in the electrolytic processing.

The amount of metal ions to be supplied to the waste electrolytic solution by electrolytic processing can be controlled by adjusting the amount of electric current in the electrolytic processing.

In a preferred embodiment of the present invention, an inorganic acid is used as a cathode liquid in the electrolytic processing of the waste electrolytic solution, and the electric conductivity of the cathode liquid is detected and adjusted.

Dilute sulfuric acid is most inexpensive and practical for use as a cathode liquid. The electrolytic reaction can be stabilized by detecting and adjusting the electric conductivity of the cathode liquid used (dilute sulfuric acid).

In a preferred embodiment of the present invention, pure water is used as a cathode liquid in the electrolytic processing of the waste electrolytic solution, and another ion exchanger is interposed between the cathode and said ion exchanger.

By interposing another ion exchanger composed of, for example, ion-exchange fibers between the cathode and the ion exchanger, it becomes possible to carry out electrolytic processing at a low voltage even when pure water having a low electric conductivity is used. Thus, a chemical such as a mineral acid may not be employed for a cathode liquid. In that case, replenishment of other inorganic components than a metal component may be effected by preparing concentrated solutions of, for example, sulfuric acid and hydrochloric acid, and supplying the solutions in such amounts as to replenish the shortage of the inorganic components.

The present invention also provides another electrolytic solution control method comprising: storing an electrolytic solution containing an organic component and an inorganic component in an electrolytic solution storage tank while controlling and keeping the electrolytic solution at a predetermined composition; removing at least part of the organic component of the waste electrolytic solution after use in electrolytic processing in an electrolytic processing apparatus; and then returning the waste electrolytic solution to the electrolytic solution storage tank.

In the case of removing part of the organic component, the main target for removal is a partially decomposed product of the organic component. The removal of such a partially decomposed product can avoid accumulation of the product in, for example, a plating solution which would adversely affect plating processing. A partially decomposed product generally has a low molecular weight. It is therefore effective to use an adsorbent having high low-molecular weight compound removal capability. The residual organic component remaining in the waste electrolytic solution can be employed as an effective additive component for e.g. a plating solution.

In the case of removing the whole organic component, the waste electrolytic solution becomes a so-called base solution with no organic component. Accordingly, when re-adding the organic component to e.g. a plating solution, the amount of the organic component to be added can be determined theoretically. Thus, a predetermined amount of organic component can be added to e.g. the plating solution by weight control or volume control without analysis of the organic component of the plating solution with an organic component analyzer. This enables very accurate addition of organic component.

The organic component may be at least one of an organic polymer compound, a sulfur compound and a nitrogen compound.

In the case of a copper sulfate plating solution for use, for example, in the production of fine interconnects by plating, the organic component to be removed includes an organic polymer compound as a suppressor, a sulfur compound as an accelerator, and a nitrogen compound as a leveler, and their decomposition products.

The removal of the organic component may be carried out by using an adsorbent.

The adsorbent may be exemplified by activated carbon. Another inorganic adsorbent, such as a zeolite, or an organic adsorbent may also be used.

In a preferred embodiment of the present invention, the removal of the organic component is carried out utilizing oxidation and decomposition of the organic component.

The organic component may be oxidized and decomposed, for example, by adding an oxidizing agent to the waste electrolytic solution or by an electrolytic method. The major part of the organic component can be decomposed into carbon dioxide and water, and the residual organic component can be removed by adsorption. This manner of removing the organic component, as compared to removal of the whole organic component by adsorption, has the advantage of decreasing the amount of a waste adsorbent containing the organic component as industrial waste.

Preferably, particles are removed from the waste electrolytic solution after the removal of the organic component.

Particles, such as those coming from the adsorbent used, are removed so as to prevent the particles from being mixed into e.g. a plating solution.

In a preferred embodiment of the present invention, the electrolytic processing apparatus is a plating apparatus which uses as an anode an insoluble electrode or an electrode not containing phosphorus.

The present invention further provides an electrolytic solution control apparatus comprising: an electrolytic solution storage tank for storing an electrolytic solution containing an organic component and an inorganic component therein while controlling and keeping the electrolytic solution at a predetermined composition; and an inorganic component adjustment apparatus for adjusting an inorganic component of the waste electrolytic solution after use in electrolytic processing in an electrolytic processing apparatus, and then returning the waste electrolytic solution to the electrolytic solution storage tank.

Preferably, the inorganic component adjustment apparatus is designed to supply metal ions to the waste electrolytic solution utilizing electrolysis.

The electrolytic solution control apparatus may further comprise an inorganic component analyzer for analyzing the inorganic component of the waste electrolytic solution introduced into the inorganic component adjustment apparatus, and feeding back the analytical results to the inorganic component adjustment apparatus.

The present invention also provides an electrolytic solution control apparatus comprising: an electrolytic solution storage tank for storing an electrolytic solution containing an organic component and an inorganic component therein while controlling and keeping the electrolytic solution at a predetermined composition; and an organic component removal apparatus for removing at least part of the organic component of the waste electrolytic solution after use in electrolytic processing in an electrolytic processing apparatus, and then returning the waste electrolytic solution to the electrolytic solution storage tank.

In a preferred embodiment of the present invention, the organic component removal apparatus includes an organic component oxidation/decomposition section for oxidizing and decomposing the organic component, and an organic component adsorption/removal section for removing the organic component by adsorption.

Preferably, the electrolytic solution control apparatus further comprises a filter for removing particles, located downstream of the organic component removal apparatus.

In a preferred embodiment of the present invention, the electrolytic processing apparatus is a plating apparatus which employs as an anode an insoluble electrode or an electrode not containing phosphorus.

According to the method and apparatus of the present invention, the composition of an electrolytic solution, such as a plating solution, can be controlled efficiently with high precision. This makes it possible to perform electrolytic processing with increased productivity and reduced cost. Further, through regeneration and reuse of a waste electrolytic solution, such as a waste plating solution, the amount of the electrolytic solution used can be decreased and also the amount of the waste liquid can be decreased, whereby the environmental burden of waste liquid can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a plating solution control system incorporating a plating solution (electrolytic solution) control apparatus according to a first embodiment of the present invention;

FIG. 2 is a schematic diagram showing an inorganic component adjustment apparatus provided in the plating solution control system shown in FIG. 1;

FIG. 3 is a schematic diagram showing another inorganic component adjustment apparatus;

FIG. 4 is a schematic diagram showing a plating solution control system incorporating a plating solution (electrolytic solution) control apparatus according to a second embodiment of the present invention;

FIG. 5 is a schematic diagram showing an organic component removal apparatus provided in the plating solution control system shown in FIG. 4;

FIG. 6 is a schematic diagram showing another organic component removal apparatus;

FIG. 7 is a schematic diagram showing yet another organic component removal apparatus;

FIG. 8 is a schematic diagram showing a plating solution control system incorporating a plating solution (electrolytic solution) control apparatus according to a third embodiment of the present invention;

FIG. 9 is a schematic diagram showing a conventional plating solution control system that employs a circulation method;

FIG. 10 is a schematic diagram showing a conventional plating solution control system that employs a batch circulation method; and

FIG. 11 is a schematic diagram showing a conventional plating system which uses a plating solution in a one-pass manner.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described with reference to the drawings. The following embodiments use as an electrolytic solution a copper sulfate plating solution comprising a base solution, which is a mixture of inorganic components such as copper sulfate, sulfuric acid, hydrochloric acid and water in a predetermined proportion, and organic additives such as an organic polymer compound as a suppressor, a sulfur compound as an accelerator and a nitrogen compound as a leveler. Further, the following embodiments use as an electrolytic processing apparatus a plating apparatus having an insoluble anode or an electrolytic copper anode not containing phosphorus. In the following description, the same or equivalent members as or to those shown in FIGS. 9 through 11 are given the same reference numerals, and a duplicate description thereof is omitted.

FIG. 1 schematically shows a plating solution control system incorporating a plating solution (electrolytic solution) control apparatus according to a first embodiment of the present invention. As shown in FIG. 1, the plating solution control system includes an inorganic component adjustment apparatus 50 for adjusting an inorganic component of a waste plating solution after use in plating in a plating apparatus 14. The plating apparatus 14 is connected to the inorganic component adjustment apparatus 50 via a waste plating solution supply line 52, and the inorganic component adjustment apparatus 50 is connected to a plating solution storage tank 12 via a waste plating solution return line 54.

A plating solution 10 stored in the plating solution storage tank 12 is supplied through a plating solution supply line 16 to the plating apparatus 14, and the waste plating solution after use in the plating apparatus 14 is supplied through the waste plating solution supply line 52 to the inorganic component adjustment apparatus 50. The inorganic component-adjusted plating solution (waste plating solution) after adjustment of the inorganic component in the inorganic component adjustment apparatus 50 is returned through the waste plating solution return line 54 to the plating solution storage tank 12. The plating solution is circulated in this manner.

The system also includes an inorganic component analyzer 58 for sampling the waste plating solution, which has been supplied into the inorganic component adjustment apparatus 50, through a sampling line 56 and analyzing the inorganic component of the waste plating solution. The analytical results are fed back to the inorganic component adjustment apparatus 50.

The inorganic component adjustment apparatus 50 according to this embodiment is designed to replenish and adjust divalent copper ions as an inorganic component of the waste plating solution. When copper plating is carried out by the plating apparatus 14 having an insoluble anode or an electrolytic copper anode not containing phosphorus, the metal component (divalent copper ions) of the plating solution gradually decreases with the progress of plating. In this regard, an insoluble anode differs from a soluble anode, and cannot replenish copper ions consumed. In the case of an electrolytic copper anode, because of a disproportionation reaction caused by dissolved monovalent copper ions, a sufficient supply of divalent copper ions is not possible. Accordingly, it is necessary for reuse of the waste plating solution to replenish the inorganic component, divalent copper ions.

With respect to the other inorganic and organic components, as with the above-described conventional system, the plating solution 10 in the plating solution storage tank 12 is sampled, and the organic and inorganic components of the plating solution 10 are analyzed by an organic/inorganic component analyzer 32. Based on the analytical results, an organic/inorganic component supply apparatus 26 is actuated to replenish the plating solution 10 with the shortage of the organic components and/or inorganic components.

The shortage of divalent copper ions can be inferred precisely from the integrated amount of electric current in the plating apparatus 14. Thus, according to this embodiment, the shortage of divalent copper ions is inferred precisely from the integrated amount of electric current in the plating apparatus 14, the shortage of divalent copper ions is supplied to the waste plating solution by the inorganic component adjustment apparatus 50, and the waste plating solution is then returned to the plating solution storage tank 12. This makes it possible to eliminate the use of a divalent copper ion analyzer for detecting a proper amount of divalent copper ions to be replenished, and control divalent copper ions in the plating solution efficiently with high precision.

As described above, the inorganic component adjustment apparatus 50 is to replenish and adjust divalent copper ions in the waste plating solution. According to this embodiment, the replenishment of divalent copper ions is effected by electrolytic processing utilizing electrolysis (anode dissolution) with the waste plating solution as an anode liquid. According to this method, unlike the method of adding metallic particles, there is no fear of particles or powder remaining in a plating solution, which particles (powder) are undesirable e.g. for the production of fine interconnects. Further, divalent copper ions in a precise amount can be supplied to the waste plating solution.

In particular, as shown in FIG. 2, the inorganic component adjustment apparatus 50 includes an electrolytic cell 60. At the both ends of the electrolytic cell 60 are disposed an anode plate 64 to be connected to the anode of a direct-current power source 62, and a cathode plate 66 to be connected to the cathode of the direct-current power source 62. The interior of the electrolytic cell 60 is separated by an ion exchanger 68, which is an ion-exchanger membrane, into an anode chamber 70 in which the anode plate 64 is located and a cathode chamber 72 in which the cathode plate 66 is located.

The waste plating solution is supplied through the waste plating solution supply line 52 into the anode chamber 70, passed through the anode chamber 70, and is discharged through the waste plating solution return line 54. During the passage of the waste plating solution through the anode chamber 70, divalent copper ions as an inorganic component are supplied to the waste plating solution. On the other hand, a cathode liquid 75, for example, dilute sulfuric acid which is most inexpensive and practical for use as a cathode liquid, stored in a cathode liquid storage tank 74, is circulated between the cathode chamber 72 and the cathode liquid storage tank 74. The electrolytic reaction can be stabilized by detecting and adjusting the electric conductivity of the cathode liquid (dilute sulfuric acid) 75.

The anode plate 64 is made of phosphorus-containing copper which is electrolytic copper doped with phosphorus in an amount of about 500 ppm. The use of such phosphorus-containing copper for the anode plate 64 has the advantage of not generating monovalent copper ions, which will cause a disproportionation reaction, when the phosphorus-containing copper dissolves.

An ion-exchange membrane having monovalent cation selectivity is used as the ion exchanger 68. In particular, the ion exchanger 68 is an ion-exchange membrane comprising a dense polymer membrane modified with, for example, a sulfonic group and also modified in the surface with, for example, quaternary ammonium. The ion exchanger 64 is, of course, not limited to such a polymer membrane.

By thus disposing the ion exchanger 68 having monovalent cation selectivity, which selectively exchanges only monovalent cation ions, between the anode plate 64 and the cathode plate 66, divalent copper ions (Cu²⁺), supplied from the anode plate 64, can be prevented from moving into the cathode chamber 72, whereby deposition of copper on the cathode plate 66 can be prevented. Hydrogen ions (H⁺) in the anode chamber 70 move through the ion exchanger 68 into the cathode chamber 72, thus passing electricity. The hydrogen ions, which have moved into the cathode chamber 72, are converted into hydrogen gas at the surface of the cathode plate 66 and the hydrogen gas is discharged out of the electrolytic cell 60. On the other hand, divalent sulfate ions (SO₄ ²⁻) in the cathode chamber 72 are shut off by the ion exchanger 68, not moving into the anode chamber 70. Accordingly, the sulfate ion concentration of the waste plating solution in the anode chamber 70 does not change.

According to this embodiment, while introducing the waste plating solution into the anode chamber 70 and introducing the cathode liquid of dilute sulfuric acid into the cathode chamber 72, a voltage is applied from the direct-current power source 62 to between the anode plate 64 and the cathode plate 66, thereby dissolving the anode plate 64 and supplying divalent copper ions to the waste plating solution introduced into the anode chamber 70. The current density at the anode plate 64 is preferably set at a somewhat high value from the viewpoint of preventing the generation of monovalent copper ions. If the current density at the anode plate 64 is made higher than 100 mA/cm², however, the anode plate dissolution efficiency can decrease due to generation of oxygen. The use of such a high current density is thus disadvantageous in the light of energy consumption. Accordingly, the current density at the anode plate 64 is preferably within the range of 10-100 mA/cm².

According to this embodiment, a copper ion concentration detector for detecting the divalent copper ion concentration of the waste plating solution in the anode chamber 70 is used as the inorganic component analyzer 58. The divalent copper ion concentration of the waste plating solution in the anode chamber 70 is detected with the inorganic component analyzer (copper ion concentration detector) 58, and based on the analytical results, the amount of the electric current flowing between the anode plate 64 and the cathode plate 66 is adjusted so as to control the amount of divalent copper ions to be supplied to the waste plating solution by the electrolytic processing.

FIG. 3 shows another inorganic component adjustment apparatus 50. This apparatus differs from the apparatus shown in FIG. 2 in that pure water is employed as a cathode liquid flowing in the cathode chamber 72, and that another ion exchanger 76 composed of, for example, ion-exchange fibers is interposed between the cathode plate 66 and the ion exchanger 68. The other construction is the same as the apparatus shown in FIG. 2.

According to this apparatus 50, it is possible to carry out electrolytic processing at a low voltage even when pure water having a low electric conductivity is used. Thus, a chemical such as a mineral acid may not be employed as the cathode liquid. In that case, replenishment of other inorganic components than a metal component may be effected by preparing concentrated solutions of, for example, sulfuric acid and hydrochloric acid, and supplying the solutions in such amounts as to replenish the shortage of the inorganic components.

FIG. 4 schematically shows a plating solution control system incorporating a plating solution (electrolytic solution) control apparatus according to a second embodiment of the present invention. According to this embodiment, an organic component removal apparatus 80 for removing at least part of the organic component of the waste plating solution is interposed in the waste plating solution return line 54, connecting the inorganic component adjustment apparatus 50 and the plating solution storage tank 12, of the preceding embodiment shown in FIG. 1. Thus, the inorganic component-adjusted plating solution (waste plating solution), whose inorganic component (divalent copper ions) has been adjusted in the inorganic component adjustment apparatus 50, is introduced into the inorganic component removal apparatus 80, where at least part of the organic component of the waste plating solution is removed, and then the waste plating solution is returned to the plating solution storage tank 12.

According to this embodiment, the organic component to be removed with the organic component removal apparatus 80 includes an organic polymer compound as a suppressor, a sulfur compound as an accelerator, and a nitrogen compound as a leveler, and their decomposition products.

In the case of removing part of the organic component with this organic component removal apparatus 80, the main target for removal is a partially decomposed product of the organic component. The removal of such a partially decomposed product can avoid accumulation of the product in the plating solution, which would adversely affect plating processing. A partially decomposed product generally has a low molecular weight. It is therefore effective to use as the below-described adsorbent 82 an adsorbent having high low-molecular weight compound removal capability. The residual organic component remaining in the waste plating solution can be employed as an effective additive component for the plating solution.

In the case of removing the whole organic component, on the other hand, the waste plating solution becomes a so-called base solution with no organic component. Accordingly, when re-adding the organic component to the plating solution, the amount of the organic component to be added can be determined theoretically. Thus, a predetermined amount of organic component can be added to the plating solution by weight control or volume control without analysis of the organic component of the plating solution with an organic component analyzer. This enables very accurate addition of organic component.

FIG. 5 schematically shows the organic component removal apparatus 80. The organic component removal apparatus 80 includes an organic component adsorption/removal section 86 comprising a container 84 packed with an adsorbent 82 such as activated carbon. According to the organic component removal apparatus 80, at least part of the organic component of the inorganic component-adjusted plating solution (waste plating solution), which has been replenished with divalent copper ions as an inorganic component in the inorganic component adjustment apparatus 50, is adsorbed onto the adsorbent 82 and thus removed from the waste plating solution, and the waste plating solution after the removal of organic component is returned to the plating solution storage tank 12.

Besides activated carbon, another inorganic adsorbent, such as a zeolite, or an organic adsorbent may also be used as the adsorbent 82.

According to this embodiment, a filter 88 for removing particles from the waste plating solution after the removal of organic component is provided downstream of the organic component adsorption/removal section 86. Particles, such as those coming from the adsorbent 82 such as activated carbon, can be removed by the filter 88, thus preventing the particles from being mixed into the plating solution.

FIG. 6 schematically shows another organic component removal apparatus 80. This organic component removal apparatus 80 additionally includes an organic component oxidation/decomposition section 94, comprising an oxidizing agent tank 92 for storing an oxidizing agent 90, located upstream of the above-described organic component adsorption/removal section 86 shown in FIG. 5. According to this removal apparatus 80, the waste plating solution, whose inorganic component (divalent copper ions) has been adjusted in the inorganic component adjustment apparatus 50, is first introduced into the oxidizing agent tank 92 and passed through the oxidizing agent in the oxidizing agent tank 92 to thereby oxidize and decompose the organic component of the waste plating solution. The major part of the organic component is thus decomposed into carbon dioxide and water. Thereafter, the residual organic component remaining in the waste plating solution is removed by adsorption in the organic component adsorption/removal section 86.

This manner of removing the organic component, as compared to the removal of the whole organic component by adsorption, has the advantage of decreasing the amount of a waste adsorbent containing the organic component as industrial waste.

FIG. 7 schematically shows another organic component removal apparatus 80. According to this organic component removal apparatus 80, the organic component oxidation/decomposition section 94 is comprised of an electrolytic apparatus 96 for electrolytically oxidizing and decomposing the organic component of the waste plating solution. The other construction is the same as the apparatus shown in FIG. 6. As with the above removal apparatus, the major part of the organic component is decomposed into carbon dioxide and water, and only the residual organic component is removed by adsorption.

FIG. 8 schematically shows a plating solution control system incorporating a plating solution (electrolytic solution) control apparatus according to a third embodiment of the present invention. This embodiment differs from the embodiment shown in FIG. 4 in that instead of providing the organic component removal apparatus 80 in the waste plating solution return line 54 connecting the inorganic component adjustment apparatus 50 and the plating solution storage tank 12, the organic component removal apparatus 80 is provided in the waste plating solution supply line 52 connecting the plating apparatus 14 and the inorganic component adjustment apparatus 50. Thus, at least part of the organic component of the waste plating solution is first removed by the organic component removal apparatus 80, and then the inorganic component (divalent copper ions) of the waste plating solution is adjusted by the inorganic component adjustment apparatus 50, and the waste plating solution is then returned to the plating solution storage tank 12.

The inorganic component adjustment apparatus 50 and the organic component removal apparatus 80 may thus be arranged in a desired order.

Although the present invention has been described in the context of control of a copper sulfate plating solution for use in plating to effect filling-in (embedding) of fine interconnect trenches and holes formed in the surface of e.g. a semiconductor substrate, the invention is also applicable to control of other plating solutions comprising organic and inorganic components, and an electrolytic solution other than a plating solution, for example, an etching solution for use in etching processing.

Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims. 

1. An electrolytic solution control method comprising: storing an electrolytic solution containing an organic component and an inorganic component in an electrolytic solution storage tank while controlling and keeping the electrolytic solution at a predetermined composition; adjusting an inorganic component of the waste electrolytic solution after use in electrolytic processing in an electrolytic processing apparatus; and then returning the waste electrolytic solution to the electrolytic solution storage tank.
 2. The electrolytic solution control method according to claim 1, wherein the adjustment of the inorganic component is effected by electrolytic processing carried out by providing a cathode chamber and an anode chamber which are separated by an ion exchanger, and using the waste electrolytic solution as an anode liquid.
 3. The electrolytic solution control method according to claim 2, wherein the ion exchanger is an ion-exchange membrane or ion-exchange fabric having monovalent cation selectivity.
 4. The electrolytic solution control method according to claim 2, wherein a soluble electrode is used as an anode in the electrolytic processing of the waste electrolytic solution, and the current density at the anode is 10 to 100 mA/cm².
 5. The electrolytic solution control method according to claim 2, wherein the concentration of metal ions in the waste electrolytic solution is detected during the electrolytic processing so as to adjust the amount of electric current in the electrolytic processing.
 6. The electrolytic solution control method according to claim 2, wherein an inorganic acid is used as a cathode liquid in the electrolytic processing of the waste electrolytic solution, and the electric conductivity of the cathode liquid is detected and adjusted.
 7. The electrolytic solution control method according to claim 2, wherein pure water is used as a cathode liquid in the electrolytic processing of the waste electrolytic solution, and another ion exchanger is interposed between the cathode and said ion exchanger.
 8. The electrolytic solution control method according to claim 1, wherein the electrolytic processing apparatus is a plating apparatus which uses as an anode an insoluble electrode or an electrode not containing phosphorus.
 9. An electrolytic solution control method comprising: storing an electrolytic solution containing an organic component and an inorganic component in an electrolytic solution storage tank while controlling and keeping the electrolytic solution at a predetermined composition; removing at least part of the organic component of the waste electrolytic solution after use in electrolytic processing in an electrolytic processing apparatus; and then returning the waste electrolytic solution to the electrolytic solution storage tank.
 10. The electrolytic solution control method according to claim 9, wherein the organic component is at least one of an organic polymer compound, a sulfur compound and a nitrogen compound.
 11. The electrolytic solution control method according to claim 9, wherein the removal of the organic component is carried out by using an adsorbent.
 12. The electrolytic solution control method according to claim 9, wherein the removal of the organic component is carried out utilizing oxidation and decomposition of the organic component.
 13. The electrolytic solution control method according to claim 9, wherein particles are removed from the waste electrolytic solution after the removal of the organic component.
 14. The electrolytic solution control method according to claim 9, wherein the electrolytic processing apparatus is a plating apparatus which uses as an anode an insoluble electrode or an electrode not containing phosphorus.
 15. An electrolytic solution control apparatus comprising: an electrolytic solution storage tank for storing an electrolytic solution containing an organic component and an inorganic component therein while controlling and keeping the electrolytic solution at a predetermined composition; and an inorganic component adjustment apparatus for adjusting an inorganic component of the waste electrolytic solution after use in electrolytic processing in an electrolytic processing apparatus, and then returning the waste electrolytic solution to the electrolytic solution storage tank.
 16. The electrolytic solution control apparatus according to claim 15, wherein the inorganic component adjustment apparatus is designed to supply metal ions to the waste electrolytic solution utilizing electrolysis.
 17. The electrolytic solution control apparatus according to claim 15, further comprising: an inorganic component analyzer for analyzing the inorganic component of the waste electrolytic solution introduced into the inorganic component adjustment apparatus, and feeding back the analytical results to the inorganic component adjustment apparatus.
 18. The electrolytic solution control apparatus according to claim 15, wherein the electrolytic processing apparatus is a plating apparatus which employs as an anode an insoluble electrode or an electrode not containing phosphorus.
 19. An electrolytic solution control apparatus comprising: an electrolytic solution storage tank for storing an electrolytic solution containing an organic component and an inorganic component therein while controlling and keeping the electrolytic solution at a predetermined composition; and an organic component removal apparatus for removing at least part of the organic component of the waste electrolytic solution after use in electrolytic processing in an electrolytic processing apparatus, and then returning the waste electrolytic solution to the electrolytic solution storage tank.
 20. The electrolytic solution control apparatus according to claim 19, wherein the organic component removal apparatus includes an organic component oxidation/decomposition section for oxidizing and decomposing the organic component, and an organic component adsorption/removal section for removing the organic component by adsorption.
 21. The electrolytic solution control apparatus according to claim 19, further comprising: a filter for removing particles, located downstream of the organic component removal apparatus.
 22. The electrolytic solution control apparatus according to claim 19, wherein the electrolytic processing apparatus is a plating apparatus which employs as an anode an insoluble electrode or an electrode not containing phosphorus. 